Finding an official ISO for Windows Server 2008 R2 is increasingly difficult as Microsoft has phased out direct public downloads for this version.
Previously available 180-day evaluation ISOs have mostly been removed from official portals but can be found in the Internet Archive . windows server 2008r2 iso
Microsoft no longer offers Windows Server 2008 R2 ISOs through official public download channels for new customers. However, if you have a valid Volume Licensing agreement or an old MSDN (now Visual Studio) subscription, you may still be able to download the ISO from the Microsoft Volume Licensing Service Center (VLSC) or the Visual Studio Subscriptions portal. Finding an official ISO for Windows Server 2008